Tumor specific molecules to aid in better diagnosis and treatment of human and animal cancer have been sought since the last century. Hard evidence of tumor-specific substances, based on molecular structural data, has been difficult to provide in most types of human cancer except those based on virally-induced cancer and involving molecular structures specified by the virus genome. There have been extremely few examples of tumor-specific molecules based on novel molecular structures. In the case of malignant human gliomas and other tumors potentially associated with amplification or changes in the epidermal growth factor receptor molecule, such as carcinoma of the breast and other human carcinomas, there have been no unequivocal demonstrations of structurally altered molecules with unique sequences.
The epidermal growth factor receptor (EGFR) is the 170 kilodalton membrane glycoprotein product of the proto-oncogene c-erb B. The sequence of the EGFR gene is known (Ullrich et al. (1984). Human Epidermal Growth Factor Receptor cDNA Sequence and Aberrant Expression of the Amplified Gene in A431 Epidermoid Carcinoma Cells. Nature 309:418-425). The EGFR gene is the cellular homolog of the erb B oncogene originally identified in avian erythroblastosis viruses (Downward et al. (1984). Close Similarity of Epidermal Growth Factor Receptor and v-erb B Oncogene Protein Sequence. Nature 307:521-527, Ullrich, et al. (1984)). Activation of this oncogene by gene amplification has been observed in a variety of human tumors (Haley et al. (1987A). The Epidermal Growth Factor Receptor Gene in: Oncogenes, Genes, and Growth Factors Edited by: Guroff, G. 12th Edition. Chapter 2. pp. 40-76. Wiley, N.Y.), and in particular, those of glial origin (Libermann et al. (1985). Amplification, Enhanced Expression and Possible Rearrangement of EGF Receptor Gene in Primary Human Brain Tumours of Glial Origin. Nature 313:144-147; Wong et al. (1987). Increased Expression of the Epidermal Growth Factor Receptor Gene in Malignant Gliomas is Invariably Associated with Gene Amplification. Proc. Natl. Acad. Sci. USA 84:6899-6903; Yamazaki et al. (1988). Amplification of the Structurally and Functionally Altered Epidermal Growth Factor Receptor Gene (c-erbB) in Human Brain Tumors. Molecular and Cellular Biology 8:1816-1820; Malden et al., (1988). Selective Amplification of the Cytoplasmic Domain of the Epidermal Growth Factor Receptor Gene in Glioblastoma Multiforme. Cancer Research 4:2711-2714).
EGF-r has been demonstrated to be overexpressed on many types of human solid tumors. Mendelsohn Cancer Cells 7:359 (1989), Mendelsohn Cancer Biology 1:339-344 (1990), Modjtahedi and Dean Int'l J. Oncology 4:277-296 (1994). For example, EGFR overexpression has been observed in certain lung, breast, colon, gastric, brain, bladder, head and neck, ovarian, kidney and prostate carcinomas. Modjtahedi and Dean Int'l J. Oncology 4:277-296 (1994). Both epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha.) have been demonstrated to bind to EGF-r and to lead to cellular proliferation and tumor growth.
One major difference between v-erb B oncogenes and the normal EGFR gene is that the viral oncogenes are amino-truncated versions of the normal receptor; they lack most of the extracytoplasmic domain but retain the transmembrane and tyrosine kinase domains (Fung et al., (1984) Activation of the Cellular Oncogene c-erb B by LTR Insertion: Molecular Basis for Induction of Erythroblastosis by Avian Leukosis Virus. Cell 33:357-368; Yamamoto et al., (1983). A New Avain Erythroblastosis Virus, AEV-H Carries erbB Gene Responsible for the Induction of Both Erythroblastosis and Sarcoma. Cell 34:225-232, Nilsen et al., (1985). c-erbB Activation in ALV-Induced Erythroblastosis: Novel RNA Processing and Promoter Insertion Results in Expression of an Amino-Truncated EGF Receptor. Cell 41:719-726; Gammett et al., (1986). Differences in Sequences Encoding the Carboxy-Terminal Domain of the Epidermal Growth Factor Receptor Correlate with Differences in the Disease Potential of Viral erbB Genes. Proc. Natl. Acad. Sci. USA 83:6053-6057). This results in a protein that is unable to bind epidermal growth factor (EGF) but can still phosphorylate other substrates (Gilmore et al., (1985). Protein Phosphorlytion at Tyrosine is Induced by the v-erb B Gene Product in Vivo and In Vitro. Cell 40:609-618; Kris et al., (1985). Antibodies Against a Synthetic Peptide as a Probe for the Kinase Activity of the Avian EGF Receptor and v-erB Protein. Cell 40:619-625), and has led to speculation that the v-erb B proteins are oncogenic because the kinase domain is unregulated and constitutively active (Downward et al., 1984).
A variety of genetic alterations can occur in viral erb B oncogenes, e.g. amino acid substitutions and deletions in the carboxy terminus of the gene. Available evidence, however, argues that the amino truncation is critical to carcinogenesis. Amino truncations are a feature of all v-erb B oncogenes, including those that arise by promoter insertion or retroviral transduction (Nilsen et al., (1985). c-erbB Activation in ALV-Induced Erythroblastosis: Novel RNA Processing and Promoter Insertion Results in Expression of an Amino-Truncated EGF Receptor. Cell 41:719-726; Gammett et al., (1986). Differences in Sequences Encoding the Carboxy-Terminal Domain of the Epidermal Growth Factor Receptor Correlate with Differences in the Disease Potential of Viral erbB Genes. Proc. Natl. Acad. Sci. USA 83:6053-6057).
In contrast, carboxy-terminal deletions appear to be associated only with tumors that arise through retroviral transduction and seem to determine host range and tumor type specificity (Gammett et al., 1986; Raines et al., (1985). c-erbB Activation in Avian Leukosis Virus-Induced Erythroblastosis: Clustered Integration Sites and the Arrangement of Provirus in the c-erbB Alleles. Proc. Natl. Acad. Sci. USA 82:2287-2291). Transfection experiments with amino-truncated avian c-erb B genes or chimeric viral oncogene-human EGF receptors demonstrates that this deletion is sufficient alone to create a transforming protein (Pelley et al., (1988). Proviral-Activated c-erbB is Leukemogenic but not Sarcomagenic: Characterization of a Replication—Competent Retrovirus Containing the Activated c-erbB. Journal of Virology 62: 1840-1844; Wells et al., (1988). Genetic Determinants of Neoplastic Transformation by the Retroviral Oncogene v-erbB. Proc. Natl. Acad. Sci. USA 85:7597-7601).
Amplification of the EGFR gene occurs in 40% of malignant human gliomas (Libermann et al., (1985) Amplification, Enhanced Expression and Possible Rearrangement of EGF Receptor Gene in Primary Human Brain Tumours of Glial Origin. Nature 313:144-147; Wong et al., (1987). Increased Expression of the Epidermal Growth Factor Receptor Gene in Malignant Gliomas is Invariably Associated with Gene Amplification. Proc. Natl. Acad. Sci. USA 84:6899-6903), Rearrangement of the receptor gene is evident in many of the tumors with gene amplification. The structural alterations seem to preferentially affect the amino terminal half of the gene (Yamazaki et al., (1985). Amplification, Enhanced Expression and Possible Rearrangement of EGF Receptor Gene in Primary Human Brain Tumours of Glial Origin. Nature 313:144-147; Malden et al., (1988). Selective Amplification of the Cytoplasmic Domain of the Epidermal Growth Factor Receptor Gene in Glioblastoma Multiforme. Cancer Research 4:2711-2714), but the nature of the rearrangements had not at that time been precisely characterized in any tumor.
Size variant EGFR genes and amplification have been reported in several human cancers. (Humphrey et al., (1988). Amplification and Expression of the Epidermal Growth Factor Receptor Gene in Human Glioma Xenografts. Cancer Research 48:2231-2238; Bigner et al., (1988) J. Neuropathol. Exp. Neurol., 47:191-205; Wong et al., (1987). Increased Expression of the Epidermal Growth Factor Receptor Gene in Malignant Gliomas is Invariably Associated with Gene Amplification. Proc. Natl. Acad. Sci. USA 84:6899-6903; and Humphrey et al. Amplification and expression of the epidermal growth factor receptor gene in human glioma xenografts. Cancer Res. 48(8):2231-8 (1988). There had been no determination, however, of the molecular basis for the altered EGFR molecules in cells.
In 1989, work of Drs. Bigner and Vogelstein elucidated the sequence of a EGF receptor mutant that has become known as the type III mutant (also referred to as delta-EGFr or EGFrvIII). This work is described in U.S. Pat. Nos. 6,455,498, 6,127,126, 5,981,725, 5,814,317, 5,710,010, 5,401,828, and 5,212,290, the disclosures of which are hereby incorporated by reference.
EGFR variants are caused by gene rearrangement accompanied by EGFR gene amplification. There are eight major variants of EGFr that are known: (i) EGFRvI lacks a majority of the extracellular domain of EGFR, (ii) EGFRvII consists of an 83 aa in-frame deletion in the extracellular domain of EGFR, (iii) EGFRvIII consists of a 267 aa in-frame deletion in the extracellular domain of EGFR, (iv) EGFRvIV contains deletions in the cytoplasmic domain of EGFR, (v) EGFRvV contains deletions in cytoplasmic domain of EGFR, (vi) EGFR.TDM/2-7 contains a duplication of exons 2-7 in the extracellular domain of EGFR, (vii) EGFR.TDM/18-25 contains a duplication of exons 18-26 in the tyrosine kinase domain of EGFR, and (viii) EGFR.TDM/18-26 contains a duplication of exons 18-26 in the tyrosine kinase domain of EGFR (Kuan et al. EGF mutant receptor vIII as a molecular target in cancer therapy. Endocr Relat Cancer. 8(2):83-96 (2001)). In addition, there is a second, more rare, EGFRvIII mutant (EGFRvIII/Δ12-13) that possesses a second deletion that introduces a novel histidine residue at the junction of exons 11 and 14 (Kuan et al. EGF mutant receptor vIII as a molecular target in cancer therapy. Endocr Relat Cancer. 8(2):83-96 (2001)).
EGFRvIII is the most commonly occurring variant of the epidermal growth factor (EGF) receptor in human cancers (Kuan et al. EGF mutant receptor viii as a molecular target in cancer therapy. Endocr Relat Cancer. 8(2):83-96 (2001)). During the process of gene amplification, a 267 amino acid deletion occurs in the extracellular domain creating a novel junction to which tumor specific monoclonal antibodies can be directed. This variant of the EGF receptor contributes to tumor progression through constitutive signaling in a ligand independent manner. EGFrVIII is not know to be expressed on any normal tissues (Wikstrand, C J. et al. Monoclonal antibodies against EGFRvIII are tumor specific and react with breast and lung carcinomas malignant gliomas. Cancer Research 55(14): 3140-3148 (1995); Olapade-Olaopa, E O. et al. Evidence for the differential expression of a variant EGF receptor protein in human prostate cancer. Br J. Cancer. 82(1):186-94 (2000)). Yet, EGFRvIII shows significant expression in tumor cells, e.g., 27˜76% breast cancer biopsies express EGFRvIII (Wikstrand, C J. et al. Monoclonal antibodies against EGFRvIII are tumor specific and react with breast and lung carcinomas malignant gliomas. Cancer Research 55(14): 3140-3148 (1995); Ge H. et al. Evidence of high incidence of EGFRvIII expression and coexpression with EGFR in human invasive breast cancer by laser capture microdissection and immunohistochemical analysis. Int J. Cancer. 98(3):357-61 (2002)), 50˜70% gliomas express EGFRvIII (Wikstrand, C J. et al. Monoclonal antibodies against EGFRvIII are tumor specific and react with breast and lung carcinomas malignant gliomas. Cancer Research 55(14): 3140-3148 (1995); Moscatello, G. et al. Frequent expression of a mutant epidermal growth factor receptor in multiple human tumors. Cancer Res. 55(23):5536-9 (1995)), 16% NSCL cancers express EGFRvIII (Garcia de Palazzo, I E. et al. Expression of mutated epidermal growth factor receptor by non-small cell lung carcinomas. Cancer Res. 53(14):3217-20 (1993)), 75% ovarian cancers express EGFRvIII (Moscatello, G. et al. Frequent expression of a mutant epidermal growth factor receptor in multiple human tumors. Cancer Res. 55(23):5536-9 (1995)), and 68% prostate cancers express EGFRvIII (Olapade-Olaopa, E O. et al. Evidence for the differential expression of a variant EGF receptor protein in human prostate cancer. Br J. Cancer. 82(1):186-94 (2000)).
The deletion of 267 amino acids with a Glycine substitution creates a unique junction that may be capable of antibody targeting. Further, in view of EGFRvIII's expression in certain tumors and its lack of expression in normal tissues, EGFRvIII may be an ideal target for drug targeting in tumor therapy. In particular, EGFRvIII would appear to be an ideal candidate for immunoconjugate therapy of tumors (e.g., an antibody conjugated to an antineoplastic agent or toxin). Another method of treatment of cancers which over-express EGFRvIII involved the use of a tumor-specific ribozyme targeted specifically to the variant receptor which did not cleave normal EGFR. The ribozyme was found to significantly inhibit breast cancer growth in athymic nude mice (Luo et al. Int. J. Cancer. 104(6):716-21 (2003)).
General antibodies for the entire EGFRvIII protein have been described. See International Patent Application No. WO 01/62931 and Kuan et al. EGF mutant receptor vIII as a molecular target in cancer therapy. Endocr Relat Cancer. 8(2):83-96 (2001), Kuan et al. EGFRvIII as a promising target for antibody-based brain tumor therapy. Brain Tumor Pathol. 17(2):71-78 (2000), Kuan et al. Increased binding affinity enhances targeting of glioma xenografts by EGFRvIII-specific scFv. International Journal of Cancer. 88(6):962-969 (2000), Landry et al. Antibody recognition of a conformational epitope in a peptide antigen: Fv-peptide complex of an antibody fragment specific for the mutant EGF receptor, EGFRvIII. Journal of Molecular Biology. 308(5):883-893 (2001), Reist et al. Astatine-211 labeling of internalizing anti-EGFRvIII monoclonal antibody using N-succinimidyl 5-[211At]astato-3-pyridinecarboxylate. Nuclear Medicine and Biology. 26(4):405-411 (1999), Reist et al. In vitro and in vivo behavior of radiolabeled chimeric anti-EGFRvIII monoclonal antibody: comparison with its murine parent. Nuclear Medicine and Biology. 24(7):639-647 (1997), Wikstrand et al. Generation of anti-idiotypic reagents in the EGFRvIII tumor-associated antigen system. Cancer Immunology, Immunotherapy. 50(12):639-652 (2002), Wikstrand et al. Monoclonal antibodies against EGFRvIII are tumor specific and react with breast and lung carcinomas malignant gliomas. Cancer Research. 55(14):3140-3148 (1995), Wikstrand et al. The class III variant of the epidermal growth factor receptor (EGFRvIII): characterization and utilization as an immunotherapeutic target. J. Neurovirol. 4(2):148-158 (1998), Wikstrand et al. The class III variant of the epidermal growth factor receptor (EGFRvIII): characterization and utilization as an immunotherapeutic target. J. Neurovirol. 4(2):148-158 (1998), Jungbluth et al. A monoclonal antibody recognizing human cancers with amplification/overexpression of the human epidennal growth factor receptor. Proc Natl Acad Sci U S A. 100(2):639-44 (2003), Mamot et al. Epidermal Growth Factor Receptor (EGFR)-targeted Immunoliposomes Mediate Specific and Efficient Drug Delivery to EGFR- and EGFRvIII-overexpressing Tumor Cells. Cancer Research 63:3154-3161 (2003)). Each of these above-mentioned antibodies, however, possess or contain murine sequences in either the variable and/or constant regions. The presence of such murine derived proteins can lead to the rapid clearance of the antibodies or can lead to the generation of an immune response against the antibody in a patient. In addition, such antibodies are relatively low affinity, on the order of 2.2×10−8 through 1.5×10−9, even after affinity maturation. (Kuan et al. EGF mutant receptor vIII as a molecular target in cancer therapy. Endocr Relat Cancer. 8(2):83-96 (2001)).
In order to avoid the utilization of murine or rat derived antibodies, researchers have introduced human antibody function into rodents so that the rodents can produce fully human antibodies. See e.g., Mendez et al. Functional transplant of megabase human immunoglobulin loci recapitulates human antibody response in mice. Nat. Genet. 15(2):146-56 (1997). This approach has been used in connection with the generation of successful antibodies directed against wild type EGFR. See e.g., Yang X et al. Development of ABX-EGF, a fully human anti-EGF receptor monoclonal antibody, for cancer therapy. Crit. Rev Oncol Hemato 38(1):17-23 (2001); Yang X-D et al. Eradication of Established Tumors by a Fully Human Monoclonal Antibody to the Epidermal Growth Factor Receptor without Concomitant Chemotherapy. Cancer Research 59(6):1236-1243 (1999); and U.S. Pat. No. 6,235,883.